1. Field of the Invention
This invention relates generally to semiconductor manufacturing, and, more particularly, to a method and apparatus for preferentially applying correction to a process control system containing multi-inputs.
2. Description of the Related Art
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Today's manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and therefore, require a number of inputs that are generally fine-tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (etching, doping, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and specialized that the processes may be performed in different manufacturing locations that contain different control schemes.
Generally, a set of processing steps is performed across a group of semiconductor wafers, sometimes referred to as a lot. For example, a process layer that may be composed of a variety of different materials may be formed across a semiconductor wafer. Thereafter, a patterned layer of photoresist may be formed across the process layer using known photolithography techniques. Typically, an etch process is then performed across the process layer using the patterned layer of photoresist as a mask. This etching process results in the formation of various features or objects in the process layer. Such features may be used as, for example, a gate electrode structure for transistors. Many times, trench isolation structures are also formed across the substrate of the semiconductor wafer to isolate electrical areas across a semiconductor wafer. One example of an isolation structure that can be used is a shallow trench isolation (STI) structure.
The manufacturing tools within a semiconductor manufacturing facility typically communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface to which a manufacturing network is connected, thereby facilitating communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script, which can be a software program that automatically retrieves the data needed to execute a manufacturing process.
FIG. 1 illustrates a workpiece (e.g., typical semiconductor wafer 105). The semiconductor wafer 105 typically includes a plurality of individual semiconductor die 103 arranged in a grid 150. Using known photolithography processes and equipment, a patterned layer of photoresist may be formed across one or more process layers that are to be patterned. As part of the photolithography process, an exposure process is typically performed by a stepper on approximately one to four die 103 locations at a time, depending on the specific photomask employed. The patterned photoresist layer can be used as a mask during etching processes, wet or dry, performed on the underlying layer or layers of material, e.g., a layer of polysilicon, metal or insulating material, to transfer the desired pattern to the underlying layer. The patterned layer of photoresist is comprised of a plurality of features, e.g., line-type features or opening-type features that are to be replicated in an underlying process layer.
Turning now to FIG. 2, a typical flow of processes performed on a semiconductor wafer 105 by a semiconductor manufacturing system is illustrated. A manufacturing system may process a set of semiconductor wafers 105 in a batch or lot (block 210). The manufacturing system may then acquire metrology data relating to the processed semiconductor wafers 105 (block 220). The manufacturing system may then analyze the metrology data to determine whether any errors detected on the semiconductor wafers 105 are outside an acceptable range of tolerance (block 230).
Upon evaluation of the errors, the manufacturing system may calculate one or more modifications to be made on one or more control input parameters that control the process operation(s) performed by the manufacturing system (block 240). Furthermore, the manufacturing system may then perform subsequent processes based upon modifications to the control input calculated above (block 250).
Among the problems associated with the current methodology includes inadvertent alteration of one control input parameter resulting from a modification made to another control input parameter. Many times, the settings of control input parameters may affect other control input parameters. Therefore, modifications made to one input parameter may affect several subsequent operations performed, some of which are unintended modifications, by the manufacturing system. Therefore, when feedback or feed-forward corrections are made to processes in the manufacturing system, inadvertent adjustments to other control input parameters may occur, leading to possible inaccuracies in processing of semiconductor wafers 105. Increased amounts of inaccuracies on the processed semiconductor wafers 105 may comprise the yield and/or performance of devices manufactured from the processed semiconductor wafers 105.
The present invention is directed to overcoming, or at least reducing, the effects of, one or more of the problems set forth above.